Silsesquioxane is a polysiloxane which has a specific structure, and is an interesting compound. Use of the silsesquioxane provides excellent heat resistance and weather resistance, so the silsesquioxane is expected to be used, for example, as a modifying agent for thermoplastic resins, an interlayer insulating film, a sealing material, a fire retardant, or a coating additive.
In view of the above circumstances, there has been an attempt to introduce various kinds of functional groups into silsesquioxane, and there has been a report on the silsesquioxane into which a group containing fluorine is introduced (see, for example, JP 2004-123698 A).
There has also been a report on a polymer having silsesquioxane (see, for example, U.S. Pat. No. 5,484,867 A). The polymer having silsesquioxane is reported to provide a polymer composition having preferably controlled thermal properties and mechanical properties which are obtained by being blended with an organic or inorganic polymer. Further, there has been a report that a polymer having silsesquioxane may have mesomorphism in some cases. Still further, there has been a report on a fluorine-containing silsesquioxane polymer and a production method thereof (see, for example, JP 2005-272506 A). The fluorine-containing silsesquioxane polymer is reported to be preferably used as a non-wetting, an antifouling treating agent and a fire retardant for fiber, a sealing material for semiconductors, or an insulating film for semiconductors.
In recent years, a silicone resin-based adhesive mainly composed of polydimethylsiloxane has been widely used as an adhesive in various applications because the silicone resin-based adhesive has excellent heat resistance, cold resistance, water resistance, weather resistance, readhesion property, and electrical insulating properties, and further has excellent adhesiveness to a polyimide, a polyamide, polytetrafluoroethylene, a silicone rubber, and the like to which general organic adhesives are hard to stick. Further, the silicone resin-based adhesive has no skin irritation which an acrylic adhesive has and has no toxicity, and therefore is used as an adhesive tape for medical use such as a bandage in recent years. For example, there has been disclosed an application for a pressure-sensitive adhesive tape such as a first aid adhesive tape (JP 07-052326 A, JP 07-008554 B, and JP 03-200885 A).
However, those silicone resin-based adhesives each have a small surface tension and extremely strong adhesiveness, so they may exert insufficient releasability when a releasing agent composed of conventional curable silicone resin is used. In particular, when released paper is stuck on an adhesive side of an adhesive tape or adhesive label, which uses an adhesive mainly composed of polydimethylsiloxane, and the adhesive tape (or label) is kept for a long period of time before use, it may be no use in some cases. The reason is as follows: when one attempts to roll out a tape from a round adhesive tape while peeling off an adhesive layer of a part of the tape which rolls out from the back face of a lower tape, or, when one attempts to peel off released paper from the adhesive side, a significant increase in peel force is caused and destruction between the adhesive layers occurs in some cases.
Accordingly, there are disclosed releasing agents to be used as separators for silicone resin-based adhesives such as a copolymer of a (polyfluoro)alkylvinyl monomer and a silane monomer having an ethylenic unsaturated bond and a silicone functional group in the molecule (JP 61-228078 A), and a composition which contains copolymers: a copolymer of fluorinated vinylidene and/or tetrafluoroethylene and another fluorine-containing monomer having an ethylenic unsaturated bond; and the copolymer used in JP 61-228078 A (JP 02-281063 A).
However, any one of the copolymers disclosed in JP 61-228078 A and JP 02-281063 A is expensive in itself. Moreover, any one of those copolymers can not dissolve in a general organic solvent such as hydrocarbon, so they are required to be dissolved in a Freon-based solvent for application. The Freon-based solvent vaporizes to cause destruction of ozone layer, and therefore the use of those copolymers is not preferable. In view of the foregoing, use of a releasing agent which can dissolve in a general organic solvent is desired. Further, the copolymer disclosed in JP 61-228078 A has problems that the copolymer has insufficient adhesiveness and coating film strength against a substrate such as a plastic film and that a release material layer itself may easily be peeled depending on conditions of use.
The inventors of the invention have conducted searches for various kinds of releasing components in view of the foregoing. As a result, the inventors of the invention have found that a fluorine-contained polymer having as essential components fluorosilsesquioxane and organopolysiloxane is excellent in releasability against a silicone resin-based adhesive. In addition, it is found to be important to improve the adhesiveness of the fluorine-contained polymer to a substrate without decreasing releasability of the releasing component in order to form a coating on the surface of a substrate such as a plastic film, glass, and a metal and to express releasing performance by using the fluorine-contained polymer. Various formulations have been examined for fixing the releasing component on the substrate. As a result, the inventors of the invention found that a conjugate, which is a conjugate of a fluorine-contained polymer containing a polymerizable monomer having a crosslinking functional group in addition to fluorosilsesquioxane and organopolysiloxane and a matrix resin having a crosslinking functional group, can be adhesive to the surface of the substrate and exert favorable releasability against general adhesives such as an acrylic adhesive, a resin for release molding, and a silicone resin. Consequently, the inventors of the invention have attained a fluorine-contained polymer composition and a surface treating agent containing the fluorine-contained polymer composition for producing a cured coating film. The cured coating film obtainable by using the surface treating agent has favorable releasability and favorable properties such as non-wetting properties, sliding properties, antifouling-properties, electrical insulating properties, transparency, chemical resistance, and heat resistance.